In the LTE-Advanced (Long Term Evolution Advanced) systems of 3GPP (3rd Generation Partnership Project), the multi-cell coordinated transmission technology is adopted to improve the service quality for cell-edge users.
ITU (International Telecommunications Union) has make a very strict requirement for the performance of IMT-Advanced (International Mobile Telecom System Advanced), which is next-generation mobile communication system. For instance, the maximum system transmission bandwidth needs to reach 100 MHz; the peak data rate of downlink and uplink data transmission needs to reach 1 Gbps and 500 Mbps. Meanwhile, the requirements for the average link spectral efficiency and the cell edge spectral efficiency is also very strict to the system.
To meet the requirement of new IMT-Advanced system, 3GPP suggests adopting multipoint coordinated transmission technology in its next-generation mobile communication system, which is LTE-Advanced, so as to improve the performance of system. The multipoint coordinated transmission technology is the cooperation between multiple transmission points which are geographically separated. Generally speaking, the multiple transmission points represent the base stations in different cells. The multipoint coordinated transmission technology is classified into downlink coordinated transmission and uplink combined reception.
The downlink coordinated transmission is classified into two categories: coordinated scheduling/beam-forming and joint transmission.
In joint transmission, all the base stations in all cells that in the set of coordinated cell send data which are the same or different to terminal by the same wireless resource block, the base stations in multiple coordination cells send the data to the same terminal at the same time. Through joint transmission, the interference signal among different cells which in LTE system are transferred into useful signal, which decreases the interference among cells and improves the performance of system.
FIG. 1 is a schematic diagram of coordinative transmission of two cells through collaborative approach in present techniques. In FIG. 1, the base stations of two cells send data to terminal at the same time, the signal sent by the base stations of the two cells are combined in the air and then received by UE (User Equipment), the interference among cells is decreased efficiently and the quality of transmission signal are improved, which increases the average spectral efficiency and the cell-edge transmission rates.
In CS/CBF (Coordinated Scheduling/Coordinated Beamforming), only UE serving cell sends data to UE, in which point is equal with the present standard and transmission mode of LTE. Other cells in the set of coordinated cell could provide service for different UE through same wireless resource block. However, in LTE standard, the base stations in each cell sending signal without taking account of the interference to the other signal sent by the base station in other cells, the sending direction and the resource of signal in cells are not coordinated. And the base station in each cell which in the set of CBF coordinated cell needs to coordinate according to the interference to the signal of other cells, so as to decrease the interference to UE in other cells as much as possible. By coordinating the direction of sending signal beam, the coordinated cells could avoid beams with large interference efficiently, which decreases the inter-cell interference and increases the quality of receiving signal.
FIG. 2 is a schematic diagram of two coordinated cells avoiding the direction of signal beam sent by serving cell through beam coordinated scheduling in present techniques.
The joint transmission requires all cells participated in coordinating obtaining data packets which is to be sent to UE. Generally speaking, the data packets of UE are transmitted from the base station of UE serving cell to the base station in UE coordinated cell through X2 interface, which costs much and become a bottleneck that restricts the application of joint transmission.
According to embodiments of the invention, the applicant found at least following problems in present technique:
In the CBF scheme, the data are only sent from UE serving cells, which avoid the high cost of transmitting data information through X2 interface. However, the timely sharing of coordination information is a prerequisite for neighbor cells to avoid beams. The time delay and the capacity of X2 interface is strictly required in sharing coordination information, which weigh heavily against the effectiveness of CBF scheme in real system.
Presently the known CBF scheme needs to transmit coordinating information in the subband of each subframe to neighbor cells, the expenses on X2 costs much, so it has difficulty in widespread availability.
Contents of the Invention
The embodiments of the invention provide a method and a device for performing space coordination among cells, which enables the pre-scheduling information of the terminal being transmitted among the base station in each coordinative transmission cell, and performing coordinated scheduling/beam-forming according to the scheduling information.
To achieve the above-mentioned purpose, on one hand the embodiments of the invention provide a method for performing space coordination among cells, which applies in mobile communication system that comprises multiple cells, one of said multiple cells is the serving cell of terminal, one or more cells of the other cells are coordinated cell of said terminal, the base station that corresponding to each said cell provide cooperative transmission service for said terminal, comprising:
The base station in said serving cell obtaining the channel information of said terminal;
The base station in the said serving cell performs pre-scheduling to said terminal, according to the acquired channel information of said terminal and the service requirement of said terminal;
The base station in said serving cell transfers the pre-scheduling information to the base station in said coordinated cell, so that the base station in said coordinated cell performs coordinated scheduling/coordinated beam-forming with the base station in said serving cell together, according to said pre-scheduling information.
On the other hand, the embodiments of the invention provide a method for performing space coordination among cells, which applies in mobile communication system that comprises multiple cells, one of said multiple cells is the serving cell of terminal, one or more cells in the other cells are coordinated cell of said terminal, the base station that corresponding to each said cell provide cooperative transmission service for said terminal, comprising:
The base station in said serving cell receiving the pre-scheduling information sent by the base station in coordinated cell and the channel information of the terminal which to be scheduled in serving cell;
The base station in said serving cell according to said pre-scheduling information and the channel information of the terminal which to be scheduled in said serving cell, performs coordinated scheduling/coordinated beam-forming.
On the other hand, the embodiments of the invention also provide a base station, which applies in the mobile communication system that comprise multiple cells, one cell of said multiple cells is serving cell of terminal, one or more cells of the other cells are coordinated cell of said terminal, the base station that corresponding to each said cell provide cooperative transmission service for said terminal, when said base station is corresponding to said serving cell, comprising:
Obtaining module for obtaining the channel information of said terminal;
Pre-scheduling module for performing pre-scheduling to said terminal based on the obtained channel information of said terminal and the service requirement of said terminal;
Sending module for transmitting the pre-scheduling information which generated by said scheduling module to the base station in said coordinated cell, so that the base station in coordinated cell could perform coordinated scheduling/coordinated beam-forming together with the base station in serving cell according to said pre-scheduling information.
On the other hand, the embodiments of the invention also provide a base station, which applies in the mobile communication system that comprise multiple cells, one cell of said multiple cells is serving cell of terminal, one or more cells of the other cells are coordinated cell of said terminal, the base station that corresponding to each said cell provide cooperative transmission service for said terminal, when said base station is corresponding to said serving cell, comprising:
Receiving module for receiving the pre-scheduling information sent by the base station in said coordinated cell and the channel information of the terminal which to be scheduled in said serving cell;
Scheduling module for performing coordinated scheduling/coordinated beam-forming based on the pre-scheduling information received by said receiving module and the channel information of the terminal which to be scheduled in said serving cell.
Compared with present techniques, the embodiment of the invention has the following advantages
With the solution of the present invention, the pre-scheduling information is transferred between base stations in various coordinated transmission cells, and the coordinated scheduling/beam-forming is performed according to the pre-scheduling information, thus, the coordinated scheduling/beam-forming is implemented with less amount of information exchange, and the spectrum efficiency of cell-edge terminal is improved.